Such a method is, for example known from EP 647,014 B1. The known method serves for ascertaining the angular position of the rotor of a brushless motor. Brushless motors are electronically commutated motors. The winding coils of these motors are energized in a cyclic sequence respectively during a predeterminable current flow angle synchronously to the angular position of the rotor. The angular position is thereby ascertained by determining the electromotive forces which are induced in the winding coils and which depend on the angular position of the rotor and by detecting the zero crossings of the electromotive forces. The determination of the electromotive forces is thereby accomplished by measuring the coil voltages present at the winding coils. Thereby, it is a detriment that the electromotive forces can be ascertained only at certain time intervals during which the respective winding coils do not carry a current. Thus, the zero crossings of an electromotive force can be determined only when these forces are present in time ranges in which the respective winding coil is not energized. Thereby, the control range of the current flow angle is substantially limited.
It is further known from EP 647,014 B1 that the angular position of the rotor can also be ascertained with special position sensors, particularly with Hall effect sensors. The position sensors and the effort and expense for the mechanical mounting of these sensors, however, represent a substantial cost disadvantage.